Rolling and annealing process



' Patented Aug. 30, 1932 UNITED STATES PATENT. OFFICE j JOHN B. TYTUS,OF MIDDLETOWN, OHIO, ASSIGNOR TO THE AMERICAN ROLLING MILL COMPANY, OFMIDDLETOWN, OHIO, A CORPORATION OF OHIO ROLLING AND ANNEALING PROCESS NoDrawing.

My invention relates to processes for the production of sheet and stripmetal of fairly thin gauge by means of a series of roll reductions andheat treatments, wherein the final product is formed from. the originalslab in single thicknesses, Without doubling or pack formation as anecessary incident.

My process relates more particularly to the production of material whichis wide as well as thin. Although I do not Wish to limit myself to anyparticular width of thin material, my invention has special applicationto the production of metal of sheet gauges with a width of, say,morethan 2024 inches.

With the use of modern machinery and modern processes of active passcontrol in the rolling mill whereby extremely heavy drafts can beobtained, it is possible to produce what has been termed sheet metal inthe trade by continuous rolling thereof in successive stands of rolls,at the rate and often in lengths comparative to the production in stripmills and skelp mills of the past.

There are certain problems, however, which attach to the production ofsheet metal at strip or skelp rates, namel (1) attainment of uniformityof gauge, 2) attainment of uniformity of temper, (3) attainment of anon-slivering surface upon deep drawing or forming. 4

The substantial width and thinness of the metal incident to continuous,high speed .hot rolling of sheets, results in variations in thickness inzones or areas of a long piece that probably arise from localizeddifferences of temperature. Where the piece is colder than at otherpoints, the rolls will not effect so much of a reduction. When a piecehaving what may be termed thick spots, is cold rolled, thepercentagedifierence in thickness will be increased rather thandecreased,.because the thick spots have a different temper from the.thin spots; further, even though the reduction were equal in amount atthick 5 and thin portions, theproportion varies in favor ofthethin-portions, and the percentage difference. in thickness is likewiseincreased.

This difiiculty, which re'sultsin unevenness of gauge, by repeated coldrolling, will produce a further unevenness of temper which Applicationfi1ed.August 21, 1929. Serial No. 387,563.

will show up in the product when any form'- ing or working is applied toit, in spite of subsequent annealing.

Furthermore, a cold rolling at the enormous pressures required, tends toproduce a surface condition which is not obviated by annealing andpickling, and which shows up when the product is bent, in the partial orcomplete breaking away of fine slivers of material.

I have found that if the hot rolling operation on a continuous or tandemmill of wide, thin pieces of metal is so controlled that even thecoldest parts of the piece are at annealing temperature at theconclusion of said hot rolling, or if the piece is raised evenmomentarily to annealing temperature, that the subse- Y quent coldrolling will largely iron out the variations in thickness, and reducethe piece to uniform gauge withoutany changes in temper which subsequenttreatment cannot eliminate. The same result may be attained by heatingthe hot-rolled product-to a normalizing-temperature prior to thecold-rolling. This may easily be accomplished in a continuous furnace.

I have further found that if, at the end of the cold rolling or beforethe final cold rolling passes, I normalize the product, the sliveringwill not occur, and that the unevenness of temper as a persistent factoris largely eliminated. ,Pickling succeeded by box annealing is usedfollowing my process as desired. Also, after normalizing it is oftendesirable to give the piece a quick pickling and washing treatment, thescale formed by normalizing being of a minimum amount.

In a co-pending application filed by me on p d prefer product at atemperature in the hot rolling mill which is within the annealing ornormalizing range; then after or before the final cold rolling passes,normalizing the product. In other words, the teaching of my invention isa step in the manufacture of high finished sheets for deep drawingpurposes which will produce uniformity of gauge, uniformity of temperand a non-slivering surface, which step comprises, in addition to allwellknown steps, normalizing and a subsequent picklin process prior tobox annealing, and

ily prior to at least a part of the cold rolling. Referring to the firstproblem, the attainment of uniformity of gauge is very' important. Thecopending application hereinabove referred to sets forth one method ofattaining it. Other efforts have comprised an attempt to produce hotrolled strip of uniform temper by finishing it on the hot millat'self-annealing tem erature; but this is diflicult of control. everalvery light passes in the cold rolls after the main cold reduction hasbeen accomplished, are also sometimes practiced, but involve obviousdisadvantages, and fail to attain a solution of the second and thirdproblems. It'is to be pointed out that a normalizing which precedes asubstantial cold reduction will enable me to produce material of uniformgauge; a

normalizing following reduction to gauge,

will not per se affect gauge. Normalizing thus solves the second andthird problems, and does this regardless of non-uniformity of gauge, andregardless of any previous treatment. It produces evenness of temper anddestroys the tendency toward slivering.

A typical procedure under my process will be to' produce a long,hot-rolled, thin, Wide strip, and then pass it through a furnace inwhich all parts of the strip are momentarilyraised'to annealing ornormalizing temperature. The piece is then given a quick picklingtreatment and washing, whereupon it is taken to the cold mills forfurther continuous reduction. After thecold rolling passes necessary tobring the piece to finished gauge, or nearly to finished gauge,have'fbeen' performed, the strip is passed through a furnace where it isbrought to a normalizing temperature, i. e., beyond the A3 point, thisnormalizing being followed by rapid cooling, whereupon a quick picklingand washing will be applied to remove the slight scale formed bynormalizing.

The piece may then be cut up into shorter sections and given aconcludingpass or passes in cold rolls or not, as desired, and thenusually will be regularly boxed annealed.

My process deals generally with ferrous metals and alloys, but moreparticularly with iron or mildsteel.

Having thus described my invention, what 1. The process of producingsheet metal,

which consists in passing a continuously hot rolled strip which has beenat normalizing temperature after the hot rolling thereof has beencompleted, through cold rolls where heavy drafts are applied thereto,resulting in a reduction of gauge, and, after a part at least of thecold rolling operation, raising the temperature of the strip above theA3 point and relatively quickly cooling said strip.

2. The process of producing sheet metal, which consists in raising acontinuously hot rolled strip to normalizing temperature, and when sameis cool, passing the strip through cold rolls where heavy drafts areapplied thereto, resulting in a reduction of gauge, and after a part atleast of the cold rolling operation, raising the temperature of thestrip above the A3 point thereafter relatively quickly cooling saidstrip.

3. The process of producing sheet metal, which consists in passing acontinuously hot rolled strip which has been at normalizing temperatureafter the hot rolling thereof has been completed, through cold rollsWhere heavy drafts are applied thereto, resulting in a reduction ofgauge, and, after a part at least of the cold rolling operation,normalizing said strip, and cleaning the strip after said normalizing.

4. The process of producing sheet metal, which consists in raising acontinuously hot rolled strip to normalizing temperature,'and when sameis cool, passing the strip through cold rolls where heavy drafts areapplied thereto, resulting in a reduction of, gauge,

and after a part at least of'the cold rolling which consists in passinga continuously hot rolled stripwhich has been at normalizing temperatureafter the hot rolling thereof has been completed, through cold rollswhere heavy drafts are applied thereto, resulting in a reduction ofgauge, and, after a part at least of the cold rolling operation,normalizing said strip, then finishing the cold rolling, and finally boxannealing the material to impart softness.

6. The process of producing sheet metal, which consists inraising acontinuously hot rolled strip to normalizing temperature, and when samevis cool, passing the material through cold rolls where heavy drafts areapplied thereto, resulting in a reduction of gauge, and after a part atleast of the cold rolling operation, normalizing said material, andafter the cold rolling box annealing the material to impart softness.

7. The process of'producing sheet metal,

temperature after the hot rolling thereof has been completed, throughcold rolls where heavy drafts are applied thereto, resulting in areduction of gauge, and, after a part at least of the cold rollingoperation, raising the temperature of the strip above the A3 point andrapidly cooling it, cleaning the strip after said heating, and after thecold rolling box annealing the material to impart softness. 8. Theprocess of producing sheet metal, which consists in raising acontinuously hot rolled strip to normalizing temperature, and when sameis cool, passing the material through cold rolls where heavy drafts areapplied thereto, resulting in a reduction of gauge, and after a part atleast of the cold rolling operation, normalizing said material, cleaningthe material after both heating oper ations, and after the cold rolling,box annealing the material to impart softness.

9. That process of producing sheet metal, which comprises continuouslyhot rolling the metal piece to thin gauge, thus producing sheet stockcharacterized by gauge and strain 2: inequalities, heating said metalabove its A3 point, and then rapidly cooling it, whereby the straininequalities are removed, and cold rolling said metal with substantialreduction, whereby the piece is reduced to uniform and finished gauge,afterward again raising said metal to a temperature above its A3 pointfollowed by a relatively rapid cooling, whereby the strain inequalitiesproduced by cold rolling said metal while of non-uniform gauge aresubstantially removed, and finishing said metal.

10. That process of producing wide sheet metal in long bands, whichcomprises hot rolling slabs to produce strip sheets characterized bygauge and strain inequalities, continuously normalizing said stripsheets, continuously picking said strip sheets, cold rolling them touniform and finished gauge with a substantial reduction, afterwardcontinuously normalizing, pickling, and finishing said strip sheets.

JOHN B. TYTUS.

